The operation of the circuit is like an enabled inverter, that is, the output Y = B provided A is high. If A is low, output is low (independent of the state of B). When the signals A and or B1 are connected to the inputs A and of this gate the output Y is....

This circuit will detect a missing pulse or abnormally long spacing between consecutive pulses in a train of pulses. The timer is connected in the monostable mode. The time delay should be set slightly longer than the timing of the input pulses. The timing....

If your ear is good, you can use this IR-pulse-to-audio converter to troubleshoot infrared remote-controls. It is also a good project for detecting infrared-light sources. A photo cell module (Radio Shack P/N 276-137) detects IR radiation and drives audio....

A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017's first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that IC normally delivers. Those....

Integrated circuit gates ICl-a and TCl-b form a monostable, whose time constant is determined by C2 and R3. When the transmitter is dekeyed (and then almost immediately rekeyed) point TX+ goes low and takes pin 1 low for a short time. This triggers the....

A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes....

The linear charging ramp is most useful where linear control of voltage is required. Some possible applications are a long period voltage controlled timer, a voltage to pulse width converter, or a linear pulse width modulator. Ql is the current source....

The automatic porch-light control circuit holds a triac on until a 4020 divider counts a number of 60-Hz powerlinc pulses. The circuit turns off a light after a predetermined time by using pins other than pin 3 of III. Various times can be set...

In microprocessor control of multiple loads, the minimum cost per load is critical. A typical application example is a large display involving driving arrays of incandescent lamps. This circuit provides minimal component cost per stage and optocoupler....

Here is a simple tachometer circuit for use with a hand-held DVM or portable chart recorder. A novel feature is that the source frequency pulse/rev rate can be directly set on a ten-turn potentiometer to provide a convenient calibration of one V per 1000....

Any dc voltage source in the 2- to 15-V range can be chopped into a unipolar square wave that has a peak amplitude nearly equal to the dc source voltage-with circuit (lightly loaded CMOS will swing within a few millivolts of each rail at low frequencies).....

This circuit converts frequency to voltage by taking the average dc value of the pulses from the 74121 monostable multivibrator. The one shot is triggered by the positive-going ac signal at the input of the 529 comparator. The amplifier acts as a dc filter,....

This zero-crossing detector uses a dual LM393 comparator, and easily controls hysteresis by the reference levels which are set on the comparator inputs. The circuit illustrated is powered by +10-V power supplies. The input signal can be an ac signal level up....

Snubber circuit R2C2, as shown, might be necessary since Rl and Cl are tailored for optimized triggering and not for dV!dt protection. Fiber-optic pairs can be used with discrete SCRs to switch thousands of volts. A photon coupler with a transistor output....

A single monostable multivibrator delays a pulse train by a variable amount; nonetheless, this amount can be no less than the minimum allowed pulse width fw· The exclusive-OR gate, IC1, generates a short pulse following every leading or falling edge of....

without significant added complexity, and a natural tendency to run away under no-load (high Q) conditions. The 20-kHz control circuit (see Fig. 2) overcomes these shortcomings hy feeding back into the asymmetrical thyristor trigger pulse generators (see....

A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017s first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that the IC normally delivers.....

At half brightness, the lamp current is pulsed on and off (Fig. 50-12b) by the voltage developed across the resistor and capacitor at the current-sense output. Lamp current is sensed by the current-sense output. A simple pulse-width modulation....

The circuit accepts two positive-voltage inputs VN and Vv and provides a TTL-compatible output pulse train whose repetition mte is proportional to the ratio VN/ V0. Full-scale output frequency is about 100 Hz, and linearity error is below 0.5 percent. The....

The time delay, T, in seconds is: T = 1.1 x Cl x (Rl + R2). The resistances are in megohms and capacitances in microfarads. The sum of R1 and R2 should not be Jess than 1000 0 nor higher than 20 MO. Pressing S1 starts the timing cycle. A low-going pulse,....

This circuit operates by charging a small capacitor from a constant-current source when the pulse to be measured is present. Dual pnp transistor Q3 is the current source; its output current equals the LM329 reference voltage divided by the resistance of....

The circuit offers independent control of initial delay and pulse rate. ICIc is connected as a pulse generator whose operation is inhibited by the normally low O/P of the ICla. When the circuit input goes low i.e., by pressing PB1, IClb O/P goes high and the....

This circuit detects frequency variation above or below preset limits. IC1 is a binary counter docked at FcLK· The outputs are comparea with switch preset values by IC2 and IC3. The input signal, which must be a positive-going pulse, is used to reset IC1.....

A sensor turns on Ql to activate the low-frequency 555 oscillator, which pulses LAMP II. Sensor may be sensitive to changes in light or temperature. Either RA or RB can be sensors, as desired. A decrease in RB or an increase in RA will cause the NE555 to....

The circuit converts frequency to voltage by taking the average de value of the pulses from the 7 4121 monostable multivibrator. The one shot is triggered by the positive-going ac signal at the input of the 529 comparator. The amplifier acts as a de....

A positive-going trigger pulse can be used to start the timing cycle with the circuit shown. In this design, trigger input pin 2 is biased to 6V (1/z Vvv) by divider Rl and R2. Control input pin 5 is biased to 8 V (213 Vvvl by the internal divider circuit.....

This circuit detects an object passing in one direction but ignores it going the opposite way. Two sensors define the sense of direction. The object blocks the light to phototransistor Ql or Q2 first dependent on the direction of approach. When the object....

This circuit produces an output pulse when SW1 (pushbutton) is depressed. It also becomes a hysteresis ga..

By varying either Rl or R2, the oscillator frequency can be adjusted over a narrow range. The R3/R4 ratio sets the second amplifier's gain to compensate for signal attenuation occurring in the phase shifters. The circuits can be driven from an external....

This simple and symmetrical free-running generator has a 50- output impedance, a pulse width of 100 ns..

As shown, three ICs are used to produce the sounds. ICl is a 555 timer that generates clock pulses. It is configured as an astable multivibrator. The frequency of the clock pulses is set by trim: mer potentiometer PI. These clock pulses are coupled to the....

A negative pulse at the input is fed via capacitor Cl to the input pin (2) of the IC, Pin 2 is held slightly above its triggering voltage of 1/3 Vcc by the voltage divider comprising Rl, R2 and RV1, The negative pulse triggers the IC and the output (pin 3)....